The invention relates to brush seals that prevent gas leakage in a turbine.
Turbines convert thermodynamic energy from fluids, such as pressurized steam, compressed air and combustion gases, into work such as to drive a generator to produce electricity. The work is performed as the fluids flow through rows of blades (also referred to as buckets) mounted on turbine wheels. The force of the fluids on the blades turns the wheels and the shaft on which of the wheels are mounted. Fluids must flow over the blades to turn the wheels and the rotor shaft. Fluids that leak into the turbine casing or otherwise do not pass over the blades do not turn the shaft and reduce the efficiency of the turbine.
To confine the fluids to the blades, seals are positioned between the stationary and rotating components of a turbine. Sealing the gaps between the stationary and rotating components is challenging due to the high temperatures and pressures of the gases flowing through the turbine. Labyrinth, honeycomb and brush seals are known types of seals for the gaps between the stationary and rotating components of an axial turbine. Brush seals are the focus of this disclosure.
A brush seal is typically arranged annularly around a rotating component of the turbine. The brush seal includes thousands of densely packed wire filaments (bristles). One end of the filaments are clamped between or welded to annular metal plates that are attached to a stationary component of the turbine. The filaments extend radially and span a gap between the stationary component and a rotating component. The tips of the filaments touch and brush against the rotating component. The closely packed filaments form a seal that prevents fluids from leaking through the gap bridged by the brush seal and between the rotating and stationary components.
Brush seals have conventionally been difficult to place where there is only a narrow space between the stationary and rotating components. The filaments in a brush seal have a length in a radial direction with respect to the turbine. A portion of the length of the filaments is needed for the annular clamp plates. The radial dimensions of the filaments and the annular clamp of a conventional brush seal do not easily fit in a narrow space between the stationary and rotating components.